How do you get a bull from a cow?

Sheer luck. A cow has to be bred to a bull, and then you wait for around 285 days to see if you get a bull or a heifer from her. It's a 50/50 chance that you'll get a bull or heifer.

You can also be sure you're going to get a bull from your cow if you artificially inseminate her with sexed semen. This means that each individual sperm that is given to her has the Y chromosome that will ensure a bull calf is born.